During its first four months of taking data, Advanced LIGO has detected gravitational waves from two binary black hole mergers, GW150914 and GW151226, along with the statistically less significant binary black hole merger candidate LVT151012. Here we use the rapid binary population synthesis code COMPAS to show that all three events can be explained by a single evolutionary channel&mdash;classical isolated binary evolution via mass transfer including a common envelope phase. We show all three events could have formed in low-metallicity environments (Z=0.001) from progenitor binaries with typical total masses &#8819;160M&#8857;, &#8819;60M&#8857; and &#8819;90M&#8857;, for GW150914, GW151226 and LVT151012, respectively.

f1: Masses of BBHs observed by aLIGO and their progenitors.Each point in the plots represents one system in our simulations. (a) Zero-age main sequence (ZAMS) masses and for GW150914 (blue—no events), GW151226 (orange) and LVT151012 (green) progenitors at Z=10%Z⊙=0.002 . We define > and so shade the non-allowed region grey. (b) Final BH masses and for merging BBHs consistent with GW150914, GW151226 and LVT151012 formed at Z=10%Z⊙. The grey diagonal dashed line shows =. The constraints we use to determine whether a merging BBHs is similar to one of the observed GW events are shown in grey and described in Results. (c) ZAMS masses and for GW150914, GW151226 and LVT151012 progenitors at the lower metallicity Z=5%Z⊙=0.001 . The progenitor masses required to produce GW151226 and LVT151012 decrease, and we are able to produce GW150914. (d) Final BH masses and for GW150914, GW151226 and LVT151012 BBHs formed from 5% solar metallicity progenitors. The panels of this figure are formatted to be comparable to Fig. 4 in Abbott et al.5.

Mentions:
We simulate events at 10% solar (Z=0.002) and 5% solar (Z=0.001) metallicity using the Fiducial model assumptions (see Methods). We select binaries which fall within the 90% credible interval on total (chirp) BBH mass and with q above the 90% credible interval lower bound for GW150914 (GW151226 and LVT151012). In all cases, we select only BBHs that merge within the Hubble time. Systems satisfying these conditions are shown in Fig. 1. The upper panel shows BBHs formed at 10% solar metallicity, whereas the lower panel shows those formed at 5% solar metallicity. The BH mass of the initially more massive star is labeled as and that of the initially less massive star as .

f1: Masses of BBHs observed by aLIGO and their progenitors.Each point in the plots represents one system in our simulations. (a) Zero-age main sequence (ZAMS) masses and for GW150914 (blue—no events), GW151226 (orange) and LVT151012 (green) progenitors at Z=10%Z⊙=0.002 . We define > and so shade the non-allowed region grey. (b) Final BH masses and for merging BBHs consistent with GW150914, GW151226 and LVT151012 formed at Z=10%Z⊙. The grey diagonal dashed line shows =. The constraints we use to determine whether a merging BBHs is similar to one of the observed GW events are shown in grey and described in Results. (c) ZAMS masses and for GW150914, GW151226 and LVT151012 progenitors at the lower metallicity Z=5%Z⊙=0.001 . The progenitor masses required to produce GW151226 and LVT151012 decrease, and we are able to produce GW150914. (d) Final BH masses and for GW150914, GW151226 and LVT151012 BBHs formed from 5% solar metallicity progenitors. The panels of this figure are formatted to be comparable to Fig. 4 in Abbott et al.5.

Mentions:
We simulate events at 10% solar (Z=0.002) and 5% solar (Z=0.001) metallicity using the Fiducial model assumptions (see Methods). We select binaries which fall within the 90% credible interval on total (chirp) BBH mass and with q above the 90% credible interval lower bound for GW150914 (GW151226 and LVT151012). In all cases, we select only BBHs that merge within the Hubble time. Systems satisfying these conditions are shown in Fig. 1. The upper panel shows BBHs formed at 10% solar metallicity, whereas the lower panel shows those formed at 5% solar metallicity. The BH mass of the initially more massive star is labeled as and that of the initially less massive star as .

During its first four months of taking data, Advanced LIGO has detected gravitational waves from two binary black hole mergers, GW150914 and GW151226, along with the statistically less significant binary black hole merger candidate LVT151012. Here we use the rapid binary population synthesis code COMPAS to show that all three events can be explained by a single evolutionary channel&mdash;classical isolated binary evolution via mass transfer including a common envelope phase. We show all three events could have formed in low-metallicity environments (Z=0.001) from progenitor binaries with typical total masses &#8819;160M&#8857;, &#8819;60M&#8857; and &#8819;90M&#8857;, for GW150914, GW151226 and LVT151012, respectively.